The invention relates to a supporting bearing for resiliently supporting parts to be connected to one another, such as the body or rear axle support and rear axle gear unit of a motor vehicle.
A supporting bearing of this type is known in which the supporting parts of the two bearing parts which rest against mutually opposite bearing surfaces of a crossmember of a vehicle body in order to support a rear axle gear unit, said bearing parts accommodating the cross-member between them, are of cup-like design. The clamping bolt, which also passes through the crossmember, being passed through the base of the bearing parts.
With the aid of the clamping bolt, the rear axle gear unit is supported in a resiliently complaint manner on the crossmember in the axial direction of the bolt via the two bearing parts.
In this arrangement, the annular elastomer element of each bearing part is vulcanized by flat front faces both to the base of the cup-like supporting part and to the flange of the pressure piece fitting over the latter, the pressure piece traversing with a neck with radial clearance the central opening of the elastomer element and the bore in the base of the associated supporting part and protruding into the crossmember bore. The annular elastomer element likewise has a radial clearance with respect to the wall of the vulcanized-on supporting part.
The fabrication of this supporting bearing is complicated since supporting part and pressure piece are to be jointly vulcanized to the elastomer element, this being possible only with the aid of a correspondingly expensive vulcanizing mould.
It is furthermore disadvantageous that the elastomer element must be highly prestressed in order to avoid one of its two bearing parts being able to lift off from its bearing surface of the part supporting the supporting bearing in the event of compressive loading of the supporting bearing. However, this cannot be avoided in the case of very high supporting forces because in this case, due to its connection to the flange of the associated pressure piece, established via the elastomer element, the cup-shaped supporting part of the relieved bearing part is lifted off, for example, from the crossmember, this causing troublesome knocks. It is also easily possible, if extreme supporting forces occur, that the collar of the supporting part will jump out of the crossmember bore, and this can lead to the collar tilting in the bore when this bearing part is loaded and the supporting part thereby being damaged or the entire bearing part no longer being able to return to its intended design position.
The necessity of highly prestressing the supporting bearing is here to the detriment of bearing softness and at the expense of the desire acoustic decoupling, which can in any case only be achieved to an unsatisfactory degree due to the relatively large contact areas between the elastomer elements and the supporting parts and pressure pieces associated with them.
The necessary axial prestressing of the elastomer elements, correspondingly hardening the supporting bearing and leading to a correspondingly steep characteristic, also lead to its inner and outer circumferential surfaces arching outwards. As a result, stress peaks occur in the elastomer material at the edge regions of the vulcanization faces, prejudicing their strength and ability to withstand sustained loading.
Finally, the bonding of the elastomer elements at both front faces by vulcanization has the consequence that the supporting bearing is only unsatisfactorily fixed in the radial direction.
An object on which the invention is based is to improve supporting bearings of the above-noted type in such a way that, in addition to a considerable simplification of their fabrication, a longer spring excursion, improving acoustic decoupling, is achieved and damaging overloading of the elastomer elements due to stress and a lifting off of the bearing part relieved during the occurrence of high supporting forces from its supporting surface are effectively prevented.
These objects are achieved according to preferred embodiments of the invention by providing an arrangement wherein a clamping bolt is provided for clamping the two bearing parts together, said clamping bolt simultaneously receiving one of the parts to be connected and traversing the bore of the other part to be connected with radial clearance so as to mutually clamp the parts to be supported resiliently relative to one another,
wherein a free front face of the elastomer element has a part-region which projects towards the front face facing it of one of the supporting part and the pressure piece to which it is not vulcanized and rests against said front face.
With this bearing construction according to the invention, the elastomer elements of the two bearing parts are thus in each case now only vulcanized by one of their front faces to the supporting part or pressure piece. These parts are therefore separated from one another and, during bearing assembly, have only to be fitted together. This separate association offers the further advantage that, in the case of very powerful jolts, the pressure piece of the bearing part experiencing relief during this process can, if its elastomer element is vulcanized to the supporting part, lift off from the elastomer element and the supporting part can thus remain on its bearing surface. A similar result is obtained if the elastomer element is vulcanized to the pressure piece. In this case, it is lifted off from the supporting part by the pressure piece.
In the intended design position, the area of contact between the elastomer elements and the supporting part or pressure piece resting against the latter is here at a minimum, this guaranteeing optimum soundproofing; not least due to the possibility of designing the bearing surface of supporting part or pressure piece in such a way that the spring excursion is long and the prestressing force correspondingly small. This offers the particular advantage that, as the compressive loading of the supporting bearing increases, the spring progression over the spring excursion is initially gradual until, from a certain spring excursion, the supporting bearing is highly stiffened by correspondingly rising progression. This pronounced spring stiffness can replace a stop limiting the spring excursion, with the advantage that it does not reach its maximum value abruptly, rather it reaches it continuously but rapidly and noise generation is thereby prevented. This progression of the spring characteristic arises from the increasingly larger bearing surface during axial loading of the bearing, under compressive stress the supporting part or pressure piece rolling against the elastomer element, its free front face portion gradually decreasing as a result. This relative movement of the surfaces resting against one another due to corresponding extension of the elastomer element produces friction and hence simultaneously vibration damping.
Furthermore, the arrangement of the invention also result in greater radial hardness of the supporting bearing, producing, under the influence of inertial forces, a better fixing of the supporting bearing.
In addition to the above-mentioned construction, from which the invention starts, a supporting bearing in accordance with German Published Unexamined Patent Application (DE-OS) 3,106,690 is already known, the construction of the two bearing parts of which is similar to that of the supporting bearing according to the invention. Their annular elastomer elements are, however, of conical design, having, due to their larger diameter, radially projecting part-regions which rest in bearing recesses formed in the beam.
Further, German Published Examined Patent Application (DE-AS) 1,163,165, in FIG. 6, discloses a supporting bearing which has two annular rubber spring elements which are supported opposite to one another against an intermediate piece and are of conical design at their front faces. The front faces which face away from each other taper conically inwards, these front faces thus each having an axially projecting outer part-region which rests against a counter-surface. However, here the intermediate piece does not form one of two parts to be supported resiliently relative to one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.